Single photon emission computed tomography (SPECT) scanning represents a large fraction of nuclear medicine procedures and is a particularly important imaging tool for diagnosing heart disease. However the diagnostic function of SPECT is limited by its low sensitivity for detecting photons. This research project concerns development of the rotating slant- hole (RSH) SPECT scanner, which is a conventional scanner with a modified collimator system. The RSH collimator allows multiple projections of the radiotracer distribution to be simultaneously imaged by the detector, and thereby has the potential to improve photon sensitivity by factors of two to four. This project focuses on evaluating a prototype RSH SPECT scanner and addressing related imaging issues. The demonstrated success of the RSH SPECT concept will lead to a widespread inexpensive enhancement of all SPECT scanners which will only involve minor hardware and software modifications. The increased photon sensitivity translates to a combination of better image resolution, reduced image noise, and reduced scanning times. Each of these developments will improve the diagnostic function of SPECT. The specific aims are: 1) to quantitatively compare the imaging performance of the RSH SPECT prototype scanner to a state-of-the- art conventional SPECT scanner; 2) to devise, implement, and evaluate a self-assessable attenuation correction method for the RSH SPECT scanner that does not use transmission measurements; and 3) to develop mathematical inversion formulas and analytic reconstruction methods for the RSlat SPECT imaging problem, and to develop algorithms to perform transmissionless attenuation- correction. The methods will involve experimentally determining task- independent imaging measures for the RSH SPECT and conventional scanners. Computer simulations and phantom measurements will be used to study attenuation correction in RSH SPECT and RSlat SPECT. Theoretical foundations for the RSlat system will be based on three-dimensional Radon transform theory.